Location: Agroecosystem Management Research2014 Annual Report
1a. Objectives (from AD-416):
Objective 1. Develop push-pull strategies for managing stable flies in agricultural systems. Sub-objective 1A. Identify stimuli that influence fly orientation and distribution. Sub-objective 1B. Develop a push-pull strategy utilizing identified attractants and repellents as components to manage flies. Objective 2. Refine the application of larval control of stable flies by studying maggot distribution, manipulation of larval habitat, and geographic extent of control required. Sub-objective 2A. Examine the causes for clumped distribution of maggots within a breeding site. Sub-objective 2B. Examine modification of soil microflora to reduce larval stable fly populations in concentrated breeding habitats. Sub-objective 2C. Determine effective radius of larval control required to see reduction below economic threshold on an individual property. The purpose of this project is to develop tools for reducing the impact of stable flies on livestock production. Three entomologists are assigned to this project, each supported by a full time research technician and one or two part time students. These scientists are members of the Agroecosystem Management Research Unit (AMRU). The AMRU is a diverse research unit with soil scientists, agronomist, agricultural engineer, and microbiologists completing the staff. The scientists assigned to this project interact with co-workers having expertise in spatial statistics, soil chemistry and physics, soil microbial ecology, and chemical synthesis and formulation to accomplish the mission of the unit.
1b. Approach (from AD-416):
Methodologies to achieve the objectives: 1) Examine the morphology and structure of sensory organs of stable fly adults and larvae. 2) Electrophysiological techniques will be used to identify attractant constituents associated with host animals (breath and skin emissions, etc.) and oviposition substrates (livestock animal manures and decomposing organic matter such as silage, rotting hay, and grass/alfalfa clippings) 3) Identify and evaluate novel repellents on stable fly populations. 4) Use visual and landscape features to develop a spatiotemporal model of stable fly dispersion that will describe and predict habitat use and suitability for larvae and adults. 5) Develop formulations of identified attractants and repellants for field application. 6) Reduce stable fly populations in confined and pastured cattle with Push-Pull strategy. 7) Take a holistic approach to reduce the development of immature stable flies by examining the biological, chemical, and physical characteristics of larval developmental sites and develop tools to modify these sites to render them unsuitable for stable fly development. Though this research will be directed at a better understanding of the stable fly habitat, other filth flies developing in similar habitats will be examined. 8) The limits of chemical and physical properties on survival of both stable flies and house flies will be studied in the laboratory. 9) Patterns of stable fly and house fly larval dispersal in relation to physical and chemical factors will be studied in the laboratory. 9) Mark release recapture studies will be performed in the field to study stable fly larval dispersal. 10) Antibiotics and food preservatives will be tested in the in the laboratory and then the field to determine their effect on stable fly survival. 11) Self marking technique will be usedat stable fly larval development sites to study the dispersal distances from these sites.
3. Progress Report:
Project #5440-32000-009-00D expired in FY2014 and was replaced by #5440-32000-010-00D. Morphology and structure of sensory organs. The morphology, location, and density of sensory receptors on the integument of stable fly and house fly larvae were characterized with scanning electron microscopy. The morphology and physiological function of distinct regions of the larval digestive system were characterized. These studies contribute to understanding how stable fly larvae orient in their environs and locate suitable microhabitats (Subobjective 2a). Larval behavior. A behavioral assay characterizing larval responses to volatile organic compounds was developed. Positive and negative controls were identified. Stable fly larvae are strongly attracted to ammonium (Subobjective 2a). Chemical ecology. We completed a scanning electron microscopy study of adult stable flies’ olfactory sensilla and found three types used for host and oviposition site localization. In electrophysiological studies, stable fly antennae responded strongly to host and environmental volatiles (Subobjective 1a). Stable fly attractants associated with cattle and their environments were identified including 1-octen-3-ol, phenol, p-cresol and m-cresol. Behavioral responses of stable flies to host associated attractants were characterized. Traps baited with attractants catch 2-4 fold more flies than unbaited traps (Subobjective 1a). Four manure associated attractants were identified and stable flies’ behavioral responses to each were characterized. Traps baited with manure associated attractants collected 3-5 times more stable flies than unbaited traps. Attractants associated with oviposition sites were identified and shown to enhance oviposition response in field trials (Subobjective 1a). A blend of natural compounds from food grade vinegar was identified that attracts house flies in agricultural environments (Subobjective 1a). We found essential oil of catnip and its active compounds, nepetalactones, to be strong spatial repellants for stable flies. Catnip oil reduced feeding by 95% and oviposition by 96%. A wax-pellet formulation containing 10% catnip oil repelled stable flies for four hours. A microencapsulated formulation of catnip oil reduced stable fly oviposition by 95% and inhibited larval growth by 90%. Field efficacy tests of an oil-based catnip formulation were conducted with pastured cattle. The repellant reduced the number of stable flies on treated animals by 80% relative to untreated animals with 24 hours of residual activity. A mixture of three natural compounds repelled stable flies and horn flies for 72 hours in laboratory tests and 48 hours in field trials (Subobjective 1b). Flies driven-away from repellent-treated cattle oriented to insecticide-treated cattle, suggesting the feasibility of the push-pull strategy for the suppression of fly populations under field conditions. Methods for incorporating attractants, oviposition stimulants, and repellants into stable fly control technologies are being explored (Subobjectives 1b). Larval community ecology. A study of the spatial variability of the substrate in a winter hay feeding site was completed. Substrate electric conductivity was mapped and then core samples were taken from representative areas for determination of water content, pH, extractable phosphate, inorganic nitrogen, total nitrogen, total carbon, and respiration rate. Emergence traps were used to correlate physical properties of the substrate with the distribution of emerging flies. Water content, pH, inorganic nitrogen, total nitrogen, total carbon, and respiration rate were positively correlated with electric conductivity and number of emerging stable flies (Subobjective 2a). Laboratory studies to determine the effects of electrical conductivity on stable fly larval development were conducted by adding 14 inorganic salts to standard laboratory diet. Electrical conductivity had little effect upon stable fly development; however, some salts, sodium chloride for example, inhibited development while others, such as potassium chloride, had little effect. In studies varying the moisture content of diets, stable fly larvae developed best in substrates with 70% moisture, but were capable of completing development in substrates with 25 - 80% moisture. The addition of ammonium bicarbonate, a food preservative, to the laboratory diet nearly doubled larval survival (Subobjective 2a). In studies of microbial succession in stable fly developmental habitats and immature stable fly phenology, we found that enteric bacteria predominate in the substrate during decomposition stages when immature stable fly population levels are highest. Enteric bacteria and immature stable fly densities decrease as the substrate decomposes (Subobjective 2b). Physical, chemical and biological characteristics (pH, moisture content, electrical conductivity, temperature, ammonium, and nitrate, and fly larvae) were characterized in weekly substrate samples from eleven stable fly larval habitats at three sites including manure, silage, and hay feeding site residues. Larvae were most active in substrates with high levels of ammonium and usually found in close proximity to the aerobic-anaerobic boundary. Larvae and substrate collected for microbial analyses have been freeze dried and roller-milled in preparation for DNA extraction and sequencing. Metagenomic analyses of larvae and substrates will be performed (Subobjective 2b). A sterile meridic larval diet for stable flies was developed and is being used as a basis for the development of a defined diet and for the identification of essential nutrients (Subobjective 2b). Stable fly larvae were dissected and examined for symbiotic organisms. A Herpetomonas sp. (currently unidentified) is ubiquitous in stable fly larvae, pupae, and adults. Although observed in all life stages at all collection sites, it was most common in larvae. We successfully cultured this organism and are in the process of verifying its identity. Also in culture are unknown species of Trichomonas and Spiroplasma isolated from stable fly larvae (Subobjective 2b). In a survey of pupal parasitoids of house flies and stable flies, we found nine species of hymenopterous parasitoids, 2 Muscidifurax, 6 Spalangia, 1 Trichomalopsis, and 1 Urolepis. Seasonal, environmental and host preferences for each species of parasitoid are being characterized (Subobjective 2b). Adult phenology. Early season adult stable flies were collected before local larval development was observed at three locations, sexed and age-graded. Older females predominated indicating they were not from local larval developmental sites (Subobjective 2c). Results of mark-release-recapture studies indicated that adult stable fly survival and dispersal were highest in June and then both decreased in July and further decreased in August. Young, unfed, flies were more likely to be recaptured than were older flies that had fed on sugar or blood prior to release. The mean time from release to recapture was 1.8 days and 90% of the recaptured flies were collected in the first 2 days after release. Half of the recaptured flies were collected more than 2.3 kilometers from their release point (Subobjective 2c). Seasonal variation of adult stable fly size was examined. Size was correlated with population level trends. Larger flies were collected when populations were increasing compared with those collected when populations were decreasing. This indicates that nutritional resources of larval developmental sites have a role in controlling population levels (Subobjective 2b). In a comparison of size between adult stable flies collected on sticky traps and those collected emerging from winter hay feeding sites we found that those emerging from the hay sites were significantly larger than the time correlated flies collected on sticky traps. These results indicate that larval developmental sites other than hay feeding sites are contributing significant numbers of flies to the adult stable fly population; even in the early summer when the hay feeding sites are most productive (Subobjective 2c). Spatial-temporal dispersion patterns of nine years of stable fly trapping data from a 25 trap grid located on 4,000 hectares of land in northeastern Nebraska were characterized. Trap catches varied greatly on temporal and spatial scales. The number of flies collected by traps was correlated with that of neighboring traps up to an inter-trap distance of 2 kilometers. Seasonal patterns of trap catches differed greatly among traps as close as 10 kilometers of each other. Some traps collected over 80% of their total annual catch by early September whereas others had collected less than 20% at that time. The analysis indicated that the 25 traps used was the minimum number needed to evaluate spatial and temporal trends in stable fly populations over the 4,000 hectare property (Subobjective 2c). Economic impact. An explicit and dynamic model of the economic impact of stable flies on cattle production in the US was developed. The model was based upon yield-loss functions relating stable fly infestation levels to cattle productivity. Using data from 2005 – 2009, cattle production losses attributable to stable flies in the US averaged $2.2 billion per year (Subobjective 2c). Control. The efficacy of insect growth regulators, Cyromazine and Novaluron, for controlling stable flies developing in winter hay feeding sites was evaluated. When applied as granular formulations at the labelled rate, both compounds reduced stable fly adult emergence by more than 90%. Residual activity of both exceeded 8 weeks. Cyromazine and Novaluron have distinct modes of action and cross resistance between them has not been reported. Therefore, rotation between these two compounds for the management of stable flies can be used to reduce the probability of the development of insecticide resistance (Subobjective 2c).
1. Immature stable flies interact with their environment through diverse sensory organs. Stable flies are a major livestock insect pest. As stable flies develop from eggs to adults they go through a number of developmental stages. Compared to adults, relatively little is known about the biology of earlier developmental stages. A better understanding of the biology of these earlier stages is important for developing control practices for reducing adult populations. ARS scientists in Lincoln Nebraska described sensory organs present on the surface of several successive developmental stages correcting previously published descriptions. Findings show that early developmental stages have sensory organs to detect temperature, moisture, pressure, taste, and smell. Comparing several developmental stages showed that at least one sensory organ developed progressively through each stage suggesting a dynamic relationship with the environment. A better understanding of the biology of developmental stages of stable fly will help identify breeding sites that can then be targeted for applying control measures that will reduce adult populations.
Chaudhury, M.F., Zhu, J.J., Sagel, A., Chen, H., Skoda, S.R. 2014. Volatiles from waste larval rearing media attract gravid screwworm flies (Diptera: Calliphoridae) to oviposit. Journal of Medical Entomology. 51(3):591-595.
Qing, Z., Zhu, J.J., Qin, Y., Pan, P., Tu, H., Du, W., Zhou, W., Baxendale, F.P. 2013. Reducing whiteflies on cucumber using intercropping with less preferred vegetables. Entomologia Experimentalis et Applicata. 150(1):19-27. DOI: 10.1111/EEA.12135.
Scott, J.G., Leichter, C.A., Rinkevihc, F.D., Harris, S.A., Su, C., Aberegg, L.C., Moon, R., Geden, C.J., Gerry, A.C., Taylor, D.B., Byford, R.L., Watson, W., Johnson, G., Boxler, D., Zurek, L. 2013. Insecticide resistance in house flies from the United States: Resistance levels and frequency of pyrethroid resistance alleles. Pesticide Biochemistry and Physiology. 107:377-384.
Zhu, J.J., Chaudhury, M.F., Tangtrakulwanich, K., Skoda, S.R. 2013. Identification of oviposition attractants of the secondary screwworm, Cochliomyia macellaria (F.) released from rotten chicken liver. Journal of Chemical Ecology. 39(11-12):1407-1414. DOI: 10.1007/S10886-013-0359-Z.
Zhu, J.J., Wienhold, B.J., Wehrle, J., Davis, D., Chen, H., Taylor, D.B., Friesen, K.M., Zurek, L. 2013. Efficacy and longevity of the newly developed catnip oil microcapsules against stable fly oviposition larval growth. Medical and Veterinary Entomology. 28:222-227. DOI: 10.1111/MVE.12029.